The time- and space scales of tropical deep convection are estimated via
analysis of 3-hourly Global Cloud Imagery (GCI) data for 3 yr at 35-70-km
resolution. The emphasis is on estimating local time- and space scales
rather than traditional zonal wavenumber-frequency spectra. This is
accomplished through estimation of local spatial lag autocorrelations, the
conditional probability of convection at neighboring points, and the expected
duration of convective events. The spatial autocorrelation scale is found to be
approximately 130 km, and the mean duration of convective events approximately
5.5 h, in the convectively active areas of the Tropics. There is a tendency
for the spatial autocorrelation scales to be shorter over the continents than
oceans (95-155 versus 110-170 km). The expected duration of convective events
likewise tends to be shorter (4-6 versus 5-7 h). In the far western Pacific,
these differences are sharp enough to legitimize the notion of the Indonesian
archipelago as an extended maritime continent with a distinctive shape.
Consistent with many other studies, the diurnal variation of the convection is
also found to be strikingly different over the continents and oceans. The
diurnal amplitude over land is comparable to the long-term mean, raising the
possibility of significant aliasing across timescales. The simple analysis of
this paper should be useful in evaluating and perhaps even improving the
representation of convective processes in general circulation models.